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218                PRACTICAL OKdANK' CIIKMISTKY

acid may be recrystallised from water or dilute at< ohol,    Yield,
about 7 grams.

Properties.  Crystallises in plates with no definite inellin^-
pointj as the acid passes into the anhydride on heating. Soluble
in alcohol and in hot water, slightly soluble in cold water.
Reactions.  Sublime a little of the acid in a trM-tubr or in u
clock glass .covered with a filter paper and funnel. I'ltthulie
anhydride sublimes in long needles, in. p. i.;<v> .
( *( )  .
C,,H4(COOIIV- C.jllt         <) i H,o,
(."()
Heat about 0*25 gram of the anhydride \\ilh 0*5 i,;rani of
rcsorcinol in a tost- tube over a small llame fora !'e\\ minutes,
so that the temperature remains at about .;.>. i 'ool, dssMiivi:
in dilute caustic soda solution, and pour inin \\.n-r. .\ ;,;nrn
fluorescence is produced, due to the formation of iluore.,a-w
(p. 187). See Af)pemU.\\ 314.
J'KKl'A RATION    105.
/^-Na'phthalenesulphonate of Sodium,  ',! IvSt >.;N;t
Merx, Weith, Av., i.S;^, 3, n^.
50 grins, naphthalene,
60           cone, sulphurie a< id.
"r,'.
The mixture is heated in a round llask (250 <\(
bath to 160  170' for four or five hours. The
poured into a basin of water (r litre j, which is heated up and
neutralised with chalk or slaked lime in the form of a thick
cream. The hot liquid is filtered through cloth, squee/rcl out,
and washed with hot water. The lilt rate is evaporated on Jt
ring-burner until a sample crystallises on cooling. The < rys-
tallinc mass of the calcium Jsalt of naphthah-ne siilplioujr arid
is filtered and well pressed. It is redissolved in hot water, and
a solution of sodium carbonate added, until the < al< sum is
just precipitated. The liquid is again filtered through < loth, or
at the pump, washed and well pressed. Tlu: filtrate ih evaporated